1. Field of the Invention
This invention relates to a paper cutting apparatus.
More specifically, it relates to an apparatus which is provided with means for controlling a back gauge so that it automatically places a pile of sheets for cutting along a predetermined series of lines.
2. Description of the Prior Art
Normally, printed stock from sheet fed presses comes in the form of a pile of sheets which is to be cut in a predetermined manner to divide the sheets into pages, coupons, or other sub-divisions. The apparatus is made up of a table on which the paper stock is laid up in a pile to a few inches high. A back gauge is movable along the table by a worm gear which can be turned manually or automatically. Normally, automatic cutters have several separate push buttons or a joystick with concealed switches to provide fast forward, slow forward, reverse, sometimes slow reverse, and stop. Push buttons or switches are connected to a control box through relays and other circuitry which, in turn, governs the direction and speed of the motor driving the worm gear. There is a clamp which presses the paper stock tightly down during the cutting, and a guillotine which descends and cuts through the pile of stock.
In the normal cutting operation, the back gauge is either manually or automatically moved to the first cutting position. The paper stock pile is laid on the table and pushed firmly against the back gauge, the stock pile clamped in position, and the mechanism actuated to cause the guillotine to descend.
A position gauge on the apparatus displays the exact position of the back gauge. There are several different types in use. One is a series of optical discs, connected through gears to the worm gear. A window shows inches and another window fractions of an inch. These discs can be mounted in a convenient place and by mirrors or other optical devices their showing may be displayed in a window in front of the machine.
A controller, which may be electronic and magnetic, or electronic and mechanical, enables the operator to store information so that the machine will move the back gauge and stop at preprogrammed positions. There are a number of ways of doing this. One is with a bar running lengthwise of the table and having a magnetic tape on its surface. One or more magnetic heads connected to the back gauge slide along the magnetic tape. The magnetic tape is marked so that when the magnetic head passes the mark signals are transmitted through the electronic circuitry to control the movement of the back gauge.
The types of controllers mentioned present certain problems. For example, a magnetic tape and magnetic head tend to become dust covered. The magnetic elements also wear out and have to be replaced. Moreover, faint signals from the magnetic head may not be strong enough to pass through the contacts of relays and connectors. Mechanical controllers are limited in their application.